Coevolution of Food Webs: Parasites, Predators and Plant Secondary Compounds

Abstract

Tropical rain forests exhibit high levels of species richness, complex food webs, strong interactions between organisms, and relatively high frequencies of mutualistic interactions. All these characteristics are thought to generate instability in food webs. We hypothesize that natural communities are stabilized by two dasses of coevolved food web interactions (animal host-parasite and herbivore-plant defense). When model food webs including these interactions are compared to equivalent webs lacking these features, they have higher proportions of feasible webs, higher frequencies of stability; and, larger proportions of stable webs with realistic predator-prey ratios and realistic return times to equilibria. Parasites and plant defenses are able to stabilize food webs involving omnivores. Food webs with mutualists can be stable if the mutualist has parasites. Parasite host specificity and herbivore specialization enhance community stability. Results of simulations are assessed in relation to the poverty of data on parasitism in tropical environments, and management of natural or regenerated conservation areas in the tropics.